This study is designed to determine if a newly recognized protein, islet amyloid polypeptide, is present in insulin secreting tumors of the pancreas and, if so, whether this protein is present in high concentration in the blood (like insulin). Also, a newly developed technique for measurement of insulin will be assessed. In the absence of suitable reagents, plasma amylin cannot be measured in any of the subjects so far studied. However, the ICMA insulin analyses are being conducted. Preliminary assessments suggest that diagnostic cutoff between relative hyperinsulinemia during hypoglycemia is a threshold of 3 mu/nl, with normals being lower and insulins being higher.